1. FIELD OF THE INVENTION
The present invention relates to a machine element such as a pipe, a tank or a coupler, a valve or the like to be attached to the pipe and tank for use in a liquid treating system, and more particularly to an art of eliminating micro-organisms from or sterilizing the system.
2. DESCRIPTION OF THE PRIOR ART
In a system for treating pure water, it is necessary to suppress propagation of micro-organisms. Similarly, in a system for treating sea water or cooling water, it is desired to suppress propagation of various marine organisms such as sea shell embryos.
However, in the pure water treating system, residual chlorine is eliminated e.g. in the course of a demineralizing process, which elimination necessarily results in undesirable propagation of micro-organisms at the water-transporting pipes or water-reserving tanks. In view to this problem, the prior art has suggested providing an ultraviolet sterilizer or an ultrafilter at such portions as above where the propagation of micro-organisms is most likely to occur. However, the effect of the sterilizer or the filter extends only within the vicinity of the unit and there still occurs organism propagation outside the vicinity. Then, in the conventional pure-water treating system, it has been a common practice to regularly sterilize the entire system passage by flushing a hot water or a diluted solution of formalin, hydrogen peroxide or the like (e.g. "Manufacturing Method of Pure Water and Superpure Water" published by Sachi Shobo).
However, the above method has some drawbacks to be described next. First, the flush-sterilizing treatment of the entire system passage requires a great deal of treatment chemical or an additional device for feeding the hot water, thereby inviting cost increase in the entire system. Second, while the treatment is being carried out, the operation of the sytem must be stopped, thereby deteriorating the system operational efficiency. Third, the effect of the treatment lasts only temporarily. That is, after a lapse of certain time period, the micro-organism propagation occurs again. Fourth, the sterilizing treatment liquid often fails to reach intricate portions of the system such as a curved piping, coupler, valve or a bolt hole, where the micro-organisms tend to remain un-sterilized and propagates significantly.
In the sea-water treating system for desalinating sea water, it has been a common practice to add chlorine to the sea water in order to suppress adherence to or growth of embryo shells on interior walls of a sea-water inlet pipe or the like (e.g. "Kogyo-yosui Binran" published by Sangyo Tosho Corp.).
However, the addition of the chlorine has an adverse influence on a polyether type reverse osmosis filter often employed in such desalinating system. Therefore, immediately before the reverse osmosis filter, a neutralizing treatment must be effected on the free chlorine in the sea water by sodium hydrogensulfite. Therefore, this method also invites system cost increase due to the addition of neutralizing liquid or unit for feeding the same.
The primary object of the present invention is to provide a machine element for use in a liquid treating system which may suppress undesirable propagation of micro-organisms inside the system for an extended period of time.